The present invention relates to electronics assemblies, and is primarily concerned with racked assemblies. Many such assemblies will be located in racks for housing in for example nineteen inch cabinets, or other size cabinets such as twenty three inch or metric cabinets. The assemblies may for instance be employed as servers for a number of systems, for example in local area networks (LANs), wide area networks (WANS), telecommunications systems or other operations such as database management or as internet servers.
Such an assembly will typically comprise a supporting frame that houses a motherboard or backplane and a number of daughterboards or module cards that extend in planes generally perpendicular to the plane of the motherboard and which are connected to the motherboard by connectors, e.g. high density connectors, so that the daughterboards can simply be introduced into the frame through an opening therein opposite the motherboard, located on guides and pushed toward the motherboard in order to connect them to it.
Each daughterboard usually requires multiple electrical connections which are generally provided by two-part multi-pin electrical connectors, one part of which is located at the rear of the daughterboard and the other part provided on the motherboard.
In order to engage the daughterboard and the motherboard connectors properly during insertion, and to aid removal of the daughterboards, it is common to employ injector/ejector mechanisms. An injector/ejector mechanism is operated by a user and is intended to ensure an appropriate even force to be applied to the electrical connectors between the motherboard and the daughterboards during insertion of the daughterboard, to lock the daughterboard in place during operation of the system and to aid disconnection of the electrical connectors during removal of the daughterboard. The most common form of injector/ejector mechanism comprises a lever arm that can be pivotally located on a flange on the frame at or adjacent to the opening or, more usually, located on the daughterboard and engage the flange, in order to provide a mechanical advantage during connection or disconnection.
One problem that has been encountered with such assemblies, however, is ensuring correct electrical connection between the daughterboards and the motherboard due to dimensional tolerances in the daughterboards and other parts of the assembly. The daughterboards may, for example, have typical dimensions in the region of 500 mm in the insertion and removal direction whereas the connectors may have a length of travel between initial contact of the pins and complete mating of the connectors, or so-called xe2x80x9cwipexe2x80x9d, as low as 0.5 to 0.8 mm, with the result that because of tolerances in the length of the daughterboards, some connectors may be overstressed while other connectors may not form a good connection. This problem is particularly severe if daughterboards toward the end of an array are relatively long and cause the flange to bow, while daughterboards at the centre of the array are relatively short.
This problem may be resolved by providing a flexible coupling in the injector/ejector mechanism to allow relative movement of a daughterboard away from the motherboard while applying a biasing force toward the motherboard. Although such a system is perfectly adequate in resolving the problem, it requires discrete components to be incorporated in each injector/ejector mechanism and is therefore relatively expensive to implement.
According to one aspect, the present invention provides an electronics assembly which comprises a frame that contains a motherboard and a plurality of daughterboards that extend in a plane generally perpendicular to the plane of the motherboard and are connected to the motherboard by means of connectors, the frame having:
(i) an opening opposite the motherboard to allow insertion of the daughterboards into the frame or removal of the daughterboards from the frame in a direction normal to the plane of the motherboard;
(ii) an injector/ejector mechanism for each daughterboard that is located on the daughterboard or the frame and engages the frame or the daughterboard respectively in a region adjacent to the opening; and
(iii) a flange that extends therealong at or adjacent to the opening and on which the injector/ejector mechanism of each daughterboard is attached or engages at different locations along the length thereof,
wherein the flange is divided into separate sections that correspond to the different locations to allow the flange to flex at any location therealong during insertion of a daughterboard without the flexing affecting the position of any adjacent location of the flange with respect to the motherboard.
According to another aspect, the present invention provides a frame for an electronics assembly which comprises a location in which a planar motherboard can be received and a plurality of guides that extend in a direction generally normal to the plane of the motherboard when it is received in the frame in order to enable a plurality of daughterboards to be located in the frame in engagement with the motherboard, the frame having:
(i) an opening opposite the location for the motherboard to allow insertion of the daughterboards into the frame or removal of the daughterboards from the frame; and
(ii) a flange that extends therealong at or adjacent to the opening and along which an injector/ejector mechanism for each daughterboard is attached or can engage at different locations along the length thereof;
wherein the flange is divided into separate sections that correspond to the different locations to allow the flange to flex at any location therealong during insertion of a daughterboard without the flexing affecting the position of any adjacent location of the flange with respect to the location of the motherboard.
The assembly and frame according to the invention enable daughterboards of different dimensional tolerances to be accommodated within the frame and biased into engagement with the motherboard in a particularly inexpensive manner since no discrete biasing components are required.
The injector/ejector mechanism for each daughterboard may, for example, comprise a lever arm that is located on the daughterboard and engages the flange or is located on the flange and engages the daughterboard. Usually the injector/ejector mechanism will be in the form of a lever arm that is pivotally attached to the daughterboard and has a relatively short (i.e. in relation to the arm) projection that engages the flange and moves the daughterboard toward the motherboard when the lever arm is moved toward the front edge of the daughterboard so that it provides a degree of mechanical advantage during insertion of the daughterboard.
Although only one injector/ejector mechanism has been referred to in respect of each daughterboard, the assembly will usually have two such mechanisms for each daughterboard, one mechanism being located at each end of the front edge of the daughterboard or on each side of the opening and the frame will accordingly have a flange on each side of the opening.
The frame will normally have a strengthening member that extends along a side thereof, and usually along both sides thereof, in the region of the opening in order to provide the frame with rigidity in the plane of the daughterboards. That is to say, the or each strengthening member will extend along the or each side of the opening in a direction normal to the plane of the daughterboards in order to reduce the degree to which the or each side of the strengthening member bows out in a direction in the plane of the daughterboards. Typically the strengthening member will extend parallel to and adjacent to the flange. It may be formed separately from the flange, for example where the flange is formed by folding a front edge portion of the material forming the sides of the frame, and attached to the sides of the frame in any appropriate manner. Alternatively, if the strengthening member and the flange are in close proximity to one another, it may be convenient to form them both from the same element. For example, they may both be formed together as a beam having a substantially xe2x80x9cCxe2x80x9d or xe2x80x9cSxe2x80x9d-shaped cross-section where one side web of the beam constitutes the flange and a web forming the other side of the beam constitutes the strengthening member.
Such a form of beam is novel per se and so, according to another aspect, the invention comprises an abutment beam for engaging a plurality of injector levers for urging daughterboards onto final engagement with a motherboard in an electronic circuit housed in a casing, the abutment beam having a first web attachable to the housing and a second web comprising a plurality of separated locations for engaging the injector levers, each location of the second web being independently flexible relative to the first web.
Whether the flange and the strengthening member are formed as separate parts or are formed together, the strengthening member is advantageously arranged on the side of the flange between the flange and the motherboard. Such an arrangement enables the injector/ejector mechanism, for example the projection of the lever arm, to bear on the flange when the daughterboard is inserted into the frame and the connectors of the daughterboard and the motherboard are mated, and also when the daughterboards are retained in position in engagement with the motherboard during operation. In this way, resilient deformation of the separate sections of the flange will exert a bias force on the daughterboards to maintain the connectors in engagement while accommodating any difference in dimensions of the daughterboards. On the other hand, no such resilient deformation is required when the daughterboards are removed and so the injector/ejector mechanism can bear on the strength member.
The flange may be divided into the separate sections by forming discontinuities such as slots or slits therein at the appropriate positions, for example by sawing or shearing. There is a relatively large degree of freedom in the depth of the slots, although to increase the distance over which the different sections of the flange may move, the depth of the slots may be as great as the flange width so that a xe2x80x9cCxe2x80x9d section beam would be cut into a corner of its cross-section. Indeed, the slot depth may be greater where the beam is attached to a side wall of the frame since the wall itself will provide rigidity in the direction of insertion or removal of the daughterboards. There is, however, not usually any advantage in increasing the depth of the slots or slits beyond the width of the flange, and where no side wall is present the strength of any strengthening member in the direction of insertion or removal will be reduced.
Other forms of assembly and frame may be employed within the scope of the invention. More than one flange and/or strengthening member may be arranged on each side of the opening, for example, or the flange and/or the strengthening member may be formed separately as beams having an xe2x80x9cLxe2x80x9d-shaped cross-section. In addition, instead of a lever arm having a single projection that bears on different surfaces (the flange and the strengthening member) for insertion and removal of the daughterboards, two projections may be provided on the lever arm that bear on opposite sides of the flange so that one projection is employed for insertion and the other is employed for removal.
It is not necessary for the flange and/or the strengthening member to be formed from the same material as each other or as the side wall of the frame but may be formed, for example, from plastics material thereby allowing a different degree of flexibility or rigidity.